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Comment by pasabagi | Hacker News Reader

What do you put in a backpack size radio? I'm struggling to imagine what could require that much space. A car battery?

Radio guts, hardware cryptography modules, power amplifiers, and batteries. They've shrunk over time but still aren't small. When I first joined the Marine Corps, we had ground radios for each of the major spectrums: HF, VHF, and UHF (LOS and SATCOM). Now, most of the radios are multi-spectrum (combined): HF/VHF and VHF/UHF/L.

The AN/PRC-117G is an example manpack radio used by the Marine Corps today. We use it for voice and data.

https://www.harris.com/solution/harris-falcon-iii-anprc-117g...

If you're not familiar with radio wave propagation, don't get suckered into thinking hand-held radios can always replace manpack radios or that manpack radios can always replace vehicle radios. The art of radio involves a balance between power, proper antenna use, and terrain. Small, hand-held radios often don't have enough power to transmit a signal the distance you may need it to go in whatever terrain the person is in.

I still don't get it. I mean - when you're talking about power supplies, there are welding power supplies that are light. A power supply is lighter by default these days because they can be made with mosfets instead of big, heavy transformers.

As for hardware cryptography modules - again - you can buy an ARM chip that's the size of your thumbnail that's basically a full blown computer.

I'd be interested to look at the insides of one. I wouldn't be surprised if making them EMP hardened would be a big component of where the bulk comes from.

Switch mode power supplies are small, but the batteries to power them are not. NSA certified crypto modules aren't in an ARM chip the size of your thumbnail.

Are SINCGARS completely defunct now?

No. Units like SINCGARS because it actually works.

a backpack sized radio can also fit a fairly high bandwidth geostationary satellite comm link. There are backpack sized radios which hold a disassembled Ku/Ka-band 1.2 meter sized satellite dish, SSPA (solid state power amplifier), BUC (baseband upconverter) and modem with 1000Base(SX,LX,T) interface. They're not very commonly seen being carried around but it's the sort of thing you might see deployed at a COP (combat outpost) or FOB in a remote part of Afghanistan. Not so much now, since the US doesn't have COPs on top of hills in random parts of Kunar province so much anymore, but they definitely exist.

examples:

http://www.c-comsat.com/antenna/flyaway-antenna-mp-100-ku-ba...

https://www.thalesgroup.com/sites/default/files/asset/docume...

http://www.tampamicrowave.com/satellite-terminals/

one of the uses for such is to give a high-resolution video feed to a platoon (or several platoon sized) group, from a drone such as the reaper, for use in their TOC (tactical operations center) of the COP/FOB. And fairly high resolution data uplink from the COP/FOB for things like hilltop mounted infrared cameras feeding data back to a larger base somewhere in the region.

I expect it's the combination of ruggedized maintainable components, maintenance spares and kit, and a lot of rechargeable cells.

When you remove the batteries, connectors, rugged case and batteries the newer radios really aren't that large. God damn they're heavy though. So glad I wasn't usually carrying the big ones on patrol. We all used smaller iComs for squad level comms.

Yeah its mostly the battery that hasn't really reduced much in size over years. Most of the other stuff is the display, antenna etc and general "soldier proofing".

Amplifiers can be large-ish if you're going over ~20W depending on how much power is going out to the antenna vs thermal dissipation requirements.

.. and if this thing is done with SDR technology (which apparently was the original aim of the program, don't know if they have backtracked since), presumably the DSP's and FPGA's are going to be larger and significantly more power hungry than bespoke ASIC's.

I believe CORBA may have been involved somewhere too, of all things...

If by "somewhere" you mean "everywhere." JTRS was fun. (Although, CORBA wasn't that bad.)

It was a memory hog though, particularly when you have 2 or 3 separate CORBA servers running.

We haven't used backpack (rucksack) sized radios for at least a decade. If by backpack you mean a typical hiking backpack you can get at REI, then yes I guess they are backpack sized.

That's good to hear.

Back in the mid-late 90's I had to travel down to Fort Gordon (? I think?) which was home of the Army Signal Corps to give a training class on using our Single Board Computers to the group that built the man-portable radio simulators.

The old guys there (and they were almost all in their 60's+) built simulators that had to weigh and behave exactly like the actual radios for effective training (except that they didn't actually transmit any signals). The radios were huge. I simply could not imagine having to lug that thing around in the field all day.

The simulators were all "programmed" using relay logic (https://en.wikipedia.org/wiki/Relay_logic), so at least the size made that easier :-)

I attended the Signal Officer Basic Course (SOBC) at Fort Gordon in 2002. Believe it or not, they didn't even have real radios to train us on at the time. We got a powerpoint presentation, which was pretty much useless.

What communication equipment they did train us on was basically obsolete. "We have to train you on the old stuff because the new training hasn't been approved yet. You probably won't see any of this in the field."

I spent weeks learning secure messaging protocols there in 2003 and never used it once... because email exists.

Rugged, overbuild, modular, multi vendor. You end up with 10 pcbs, one per function/module while similar radio on civilian market has pretty much ~3-5 main silicon packages.

Doesnt mean milspec cant be light when requirements arent ridiculous, http://www.milspec.ca/radspec/prc-343.html is build like something off the shelf.

1990's era "Software Defined Radio" ... sounds like it's running Windows, using CORBA?!

Yeah what's up with that? It reads like a requirement written to be fulfilled by a specific vendor with an already identified offering.

CORBA was the rage back in the 1990s. CORBA, WebObjects, and COM all were part of the push to package services into “replaceable components” (like microservices today).

Probably not Windows. These radios require a POSIX compliant OS. In the old ones (not the latest spec) the only allowed external calls were to CORBA services and POSIX capabilities. This was to aid portability (discussed in TFA: didn't help because changing capabilities usually required hardware and firmware changes, not just software).

http://www.public.navy.mil/jtnc/Pages/resources.aspx?filter=...

Windows 2000 was just barely POSIX compliant for defense purposes.

I worked on the handheld JTRS radios some years ago, it was running Green Hills Integrity RTOS at the time.

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